To provide an accessory-attaching device to a peripheral appliance of an endoscope with which an accessory can be freely fitted at an arbitrary angle/location to an appliance body of the peripheral appliance of the endoscope, and convenience when the accessory is used can be increased.

This accessory-attaching device is equipped with a plurality of protrusions 11 to 15 for attaching the accessory, which are provided on the external surface of the peripheral appliance of the endoscope 1, and an accessory-holding member 6 having a shape for fixing the accessory by utilizing the protrusions 11 to 15. The accessory 40 can be attached at an arbitrary angle by changing the combination of the protrusions 11 to 15 which are used when the accessory-holding member 6 is attached.